Hydraulic transmitter



Dec. 23, 1952 P. E. THOMAS HYDRAULIC TRANSMITTER Filed May 25, 1947 5 Sheets-Sheet l "Dec. 23, 1952 P. E. THOMAS HYDRAULIC TRANSMITTER 3 Sheets-Sheet 2 Filed May 25, 1947 a a 6 4 3 d wy z Dec. 23, 1952 P. E. THOMAS 2,622,393

HYDRAULIC TRANSMITTER Filed May 23, 1947 s Sheets-Sheet s Patented Dec. 23, 1952 HYDRAULIC TRANSMITTER Percival Edward Thomas, Worcester Park, England, assignor to Sterling Industries Limited,

London, England Application May 23, 1947, Serial No. 150,088 In Great Britain May 29, 1946 4 Claims.

This invention relates to transmitters for use in hydraulic transmission systems.

The main object of this invention is to provide an improved arrangement of transmitter which, when incorporated in an hydraulic transmission system, will enable that system to be charged or primed by operation of the transmitter itself.

A further object is to provide an improved transmitter which will enable the liquid in a transmission system to be maintained under pressure, despite loss which may occur due to leakage.

A still further object is to provide a transmitter which will enable the system in which it is fitted to be bled by operation of the transmitter itself.

According to the present invention there is provided an hydraulic transmitter which comprises a pump, the working chamber of which is connected to a transmission line and the movable pumping element of which has an opening connecting the working chamber with a liquid chamber having in it a displacer provided itself with an opening connecting the liquid chamber to a reservoir for liquid. The movable element of the pump is so spring connected to the displacer element that movement of the movable element on its transmission stroke tends to move the displacer with it into the liquid chamber to a limiting position; and the opening in the movable pumping element is controlled by a non-return valve arranged to close the opening when the movable element is moved on its transmission stroke, while the opening in the displacer is controlled by a nonreturn valve arranged to close the opening when the movable element is moved on its return stroke.

Where such a transmitter is incorporated in a transmission system including the familiar receiver which is biased as by a spring to a datum position, it is possible as is fully described hereinafter, to prime the system with liquid at a predetermined pressure by operations of the transmitter itself, the arrangement being such that this pressure is automatically maintained.

The invention is illustrated in the accompanying drawings, in which:

Figure 1 is a longitudinal sectional plan, taken on line I--I of Figure 2;

Figure 2 is a longitudinal sectional elevation;

Figure 3 is an end elevation looking in the direction of the arrow III of Figure 2, but showing apart in section; and I Figure 4 is a transverse section on the; line IV-IV of Figure 2.

Referring to the drawings, I indicates a transmitter or pumping element or plunger, which is slidable in a cylinder 2 and has a blank pressure end 3 fitted with a non-return valve 4 to close discharge openings 4'. The transmitter I is fitted with a pin 5 extending at each end beyond the transmitter and through slots 6 formed in the wall of the cylinder 2 where the ends of the pin are fitted with rollers 'I to be engaged by bifurcated operating arms 8 secured to an operating rock-shaft 9.

Slidable on the transmitter I is a displacer I0 and both the transmitter plunger I and this displacer I8 are hollow and thus provide conjointly a chamber II for pressure liquid; the displacer I9 is controlled by a spring I2 which urges the displacer on the transmitter I so as to tend to decrease the volume of the chamber II.

The operating face of the pumping elemen I opens into a sub-chamber I3 having an outlet union Id for connection to the transmission line 24. I

This line extends in the usual way to a receiver which is to be controlled by the transmitter, such a receiver being diagrammatically shown in Figure 2 as comprising a cylinder 25 having slidable in it a plunger 26 urged by a spring 21 against the pressure transmitted through the line 24 by the transmitter plunger I, this spring being of suiicient strength to overcome the action of the spring I2. The term receiver is employed as is usual in the art, to denote apparatus which is to be actuated, by operation of the transmitter, for the purpose of effecting some control: for example, by the displacement of the plunger 26.

The non-return valve 4 is disposed to close automatically when the pumping element I is moved on its transmission stroke, i. e. to the left as seen in Figure 1.

The displacer III is formed With openings I6, placing the chamber II in communication with a reservoir I'I formed by the casing III of the transmitter, the openings I5 being controlled by a non-return valve I5 disposed to close when the pumping plunger I moves on its return stroke under the action of the pressure in the transmission line Id.

The system incorporates in the usual manner a normally closed bleed valve by which the system can be freed from air. It is preferred to dispose the bleed valve at a point adjacent the transmitter so that it can be operated by ithevoperator stationed at the transmitter: in the form'shown in the drawings this is achieved by incorporating the bleed valve indicated at 20 as part of the transmitter, the valve terminating a bleed line I9 which extends as shown in Figure 2 from the remote part of the system, the valve 20 being freed for the bleeding operation or normally locked by a screw plug 2| as shown in Figure 3: the valve 20 when freed enables air and liquid to pass into the reservoir I'I having itself a closure plug 22 which forms a filler plug for the reservoir and which can be removed to allow the free escape of air through a passage 23 during the priming operation.

The parts are shown in Figures 1 and 2 in full lines in positions they would occupy in normal use when the system is primed: in this condition the chamber II as well as the subchamber I3 and the line I4 will be charged with liquid which however is not shown in the drawing: when however the system is empty or requires replenishment, the displacer Illwill be drawn by the spring I2 to the dotted line position shown in Figures 1 and 2, in which position the displacer I abuts the end of the cylinder 2.

Assuming the system to be empty, it can be primed with liquid by repeated operation of the plunger I, it being assumed that'the bleed valve 20 is opened. The system being empty, the displacer It will be drawn by the spring I2 against the end of the cylinder 2. The plunger I is shown in the drawing at the end of its return movement so that when it is moved forward (i. e. to the left as seen in Figure 1), liquid will be drawn into the chamber II which increases its volume, past the non-return valve I5 from the reservoir I1. When the plunger is returned (i. e. is moved to the right as seen in Figure 1), this liquid or at least somelpart of it will flow into thetransmission line past the valve 4 which opens during this return movement. Repeated strokes of the plunger gradually fill the system, the liquid being trapped inthe system by closing of the valve 4. Liquid is prevented from returning to the reservoir I! by the valve I5 which opens only while the plunger I moves forward when the displacer I8 is held against forward movement and so creates a'drop in pressure in the chamber II by the closing of the valve 3.

When it is judged that the transmission has been bled, the bleed valve is closed in the usual manner leaving a column of liquid between the pressure face of the plunger I and the pressure face of the receiver 25--2'I.

By now continuing the pumping action of the plunger I, the forward movement of the plunger will move the receiver against its bias but will still cause liquid to be drawn into the chamber II past the valve I5. On the return stroke, the pressure reaction of the receiver will be transmitted back through the liquid in the line and will hold the valve 4 closed; the liquid in the chamber II being trapped by the valve I5 will now operate to displace the displacer Iii against the action of itsspring I2 up to a limit, depending on the value of the spring I2. Continued operation of the plunger I will now cause the plunger and the displacer Iii to move together as a unit resulting in normal transmission to the system and hence to the receiver.

The spring I2 of course, operatesto hold the liquid in the chamber II under pressure so that should the pressure in the transmission line fall below it due to leakage for example, the displacer will be drawn on by the spring I2 to force liquid past the valve 4 to replenish loss. When the displacer I0 reaches the limit of its travel under the urge of the spring I2, then the chamber II will be recharged and the spring loaded to maintain the desired pressure in the transmission; the spring I2 would be chosen to hold the liquid under a pressure above atmospheric pressure so that not only would any loss by leakage be made good but also air is prevented from entering the system.

It will be clear that for the purpose of insuring thatunder all operating conditions the chamber II shall become charged with liquid it is essential that a limit be imposed on this movementof the displacer I 6 and this is effected of course by arranging the left-hand end of the displacer Is to abut in the limiting position against the right-hand end of the cylinder 2, this being the position of the parts shown in dotted lines in Figure 1. Without such a limit, it wouldbe impossible to-rely on the movement of the plungeri withrespect to the displacer Iii which is necessary to insure that increase in volume of the chamber I I which is essential to cause liquid to be drawn-through the valve it into the chamber II during the stroke of the piston to the left.

Summary 0 operation Normally, the parts, with the exception of the valve 4, Will be in the positions shown in Figures 1, 2 and 3, the bleed valve 26 being closed, and the fluid system comprising the chamber II, the sub-chamber IS, the pipe I4, and the receiver space to the right of the plunger 25 being filled with liquid. The reservoir I! will be partially filled with liquid, at least to a level above the inlet passages or openings IS. The valve 4 will be closed rather than open as shown in Figure 1. When the transmitter plunger I is moved to the left, it will force fluid from the sub-chamber I3 through the transmission line 24 to the receiver, causing the receiver piston 26 to move to the left, compressing the spring 27. The spring I2 will cause the displacer It toiollow the transmitter plunger I, the valve l5 will remain closed, and the fluid in the chamber II will remain unchanged in volume as a fixed mass offiuid. Since the displacer It Will move with but not relatively to the plunger l, the displacer will not engage the cylinder 2.- The returning of the transmitter plunger I will permit the receiver plunger 26 to move to the right to 'maintain pressure in the line I4 and chamber I3, and thus maintain the valved closed. The displacer II) will move together with the transmitter plunger I without changing its position relative to the plunger I, and the valve I5 will remain closed. Hence, the body of fluid in the chamber II will remain constant.

Should fluid become lost, as by leakage from the transmission, the pressure in the line 24 and sub-chamber 53 will be maintained bythe spring I2 which will move the displacer ID toward the left relatively to the transmitter plunger I, thereby discharging some fluid from the chamber II past the valve 4 intothe subchamber I3, until pressure has been built "up in the sub-chamber I3 to sucha'value as to cause the valve 4 to close. Consequently, the volume of fluid in the chamber II will be reduced, and the displacer I0 will be in a position on the transmitter plunger lvmore' to the left than as shown in Figure 1.

This action will continue as loss of fluid continues until the left end of the displacer I9 again engages the right end of the cylinder 2 so as to arrest leftward movement of the displacer I while the transmitter plunger I continues to move to the left. The relative separating movement of the displacer I0 and transmitter plunger I thus effected will increase the volume of the chamber II so as to open the valve I and permit fluid to enter the chamber II from the reservoir II. In this way, the displacer I0 and transmitter plunger I will be restored to the relative positions shown in Figure 1 with the chamber II then completely filled with liquid.

During continuous or intermittent delivery of fluid under pressure from the receiver to an extraneous point, the relative movement between the displacer III and the transmitter plunger I will be caused intermittently to take place in the manner described above so as to maintain in the chamber I I sufficient fluid to replenish the fluid delivered from the receiver to the extraneous point.

If the system comprising the chambers II and I3, the transmission line 24, and the receiver 25262'I should be completely empty of liquid, the displacer II! will be held'toward the left by the spring I2, so that the left end of the displacer will abut the right end of the cylinder 2. In order to fill the system with liquid and restore the displacer I0 and the plunger I to their normal relative operating positions shown in Figure 1, the bleed valve plug 2I is unscrewed to open the bleed valve 20, the plug 22 is unscrewed, and the transmitter plunger I is reciprocated. When the plunger moves to the left, the displacer II! will remain stationary because of its engagement with the right end of the cylinder 2, and the increasing of the volume of the chamber II thereby effected will cause the valve I5 to open so as to permit fluid to flow from the reservoir I'I into the space II. Air contained in the sub-chamber I3 will be forced out through the transmission line 24, past the receiver 25-26--2I, through the bleed line I9, past the bleed valve 20, through the opening 23, and the opening then uncovered by removal of the plug 22. On the rightward movement of the plunger I, the spring I2 will, for a time, hold the displacer I0 stationary thereby causing a decrease in the volume of the chamber II and a discharge of fluid from this chamber past the valve 4 into the subchamber I3 and thence into the transmission line 24. When the plunger I again moves toward the left, more fluid will be taken into the chamber I I through the valve I5, and on the next rightward stroke of the plunger fluid will be discharged into the sub-chamber I3 and thence into the transmission line 24. Repeated operations of this kind ultimately will cause the chamber II, the sub-chamber I3, the receiver, and the bleed line to be filled with liquid. The bleed valve 20 may then be closed, the plug 22 replaced, and the apparatus operated in the normal manner previously described.

What I claim is:

1. An hydraulic transmitter comprising 2. cylinder, a plunger in the cylinder connected at one end of said cylinder to a transmission pipe line, a displacer forming conjointly with said plunger and the other end of the cylinder a liquid-receiving chamber, the plunger having an opening for connecting the said one end of the cylinder to the liquid receiving chamber, a reservoir for liquid, the displacer having an opening for connecting the said chamber to the reservoir, means to reciprocate the plunger, spring means so connecting the plunger and the displacer that transmission movement of the plunger tends to move the displacer with it, means to limit such movement of the displacer, a non-return valve to close the opening in the plunger when the plunger is moved on its transmission stroke and a non-return valve to close the opening in the displacer when the plunger moves on its return stroke.

2. An hydraulic transmitter comprising a cylinder open for connection to an hydraulic transmission pipe line, a hollow plunger, a hollow displacer slidable on the plunger, the plunger and displacer defining a chamber between them, means to move the plunger on its transmission stroke, means resiliently connecting the plunger to the displacer so that transmission movement of the plunger tends to move the displacer with it, a passage in the plunger connecting the chamber to the transmission connection of the cylinder, at non-return valve in said plunger to close the passage when the plunger moves on its transmission stroke, a reservoir for liquid, a passage in the hollow displacer to connect the chamber to the reservoir, and a nonreturn valve to close the passage in the displacer when the plunger moves on its return stroke.

3. An hydraulic transmitter comprising a transmission pipe line connection, a liquid reservoir, a chamber, a pump having a movable pumping element interposed between said transmission pipe line connection and said chamber, a displacer interposed between said chamber and said liquid reservoir, spring means so connecting the pumping element and the displacer to one another that pumping movement of the pumping element tends to move the displacer with it, means to limit such movement of the displacer, the pumping element having a through opening for providing communication between said pipe line connection and said chamber and the displacer element having a through opening for providing communication between said chamber and said reservoir, valve means to close the opening in the pumping element when that element moves on its transmission stroke, and valve means to close the opening in the displacer element when the pumping element moves on its return stroke.

4. An hydraulic transmitter as claimed in claim 3, and having also a connection for a bleed line, the said connection having a valve to open the connection to the reservoir.

PERCIVAL EDWARD THOMAS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,241,112 Bowen May 6, 1941 2,294,976 Gardiner Sept. 8, 1942 2,335,748 Fowler Nov. 30, 1943 FOREIGN PATENTS Number Country Date 414,047 Great Britain July 4, 1934 

